Your Most Pressing Nutrition Questions, Answered!

To celebrate the second anniversary of the Nutrition Diva podcast, I'm devoting this week’s column to answering some of the many interesting questions that readers have sent over the last two years.

Is Kombucha Good For You?

I’ve gotten at least a dozen questions about kombucha, a fermented beverage that’s often said to have miraculous health-enhancing or curative powers. Here’s the scoop on kombucha:

Kombucha is tea that’s been fermented with yeasts and bacteria. Fermented foods like yogurt, kefir and kombucha contain friendly bacteria that help keep your digestive system healthy. However, kombucha is not a miracle tonic or a cure for anything, and the FDA has begun sending warning letters to manufacturers and distributors who are making unsupported health claims.

Commercial kombucha products are often high in sugar and I suggest limiting your consumption of sweetened beverages—even those dressed up as health foods.

Are Green Potatoes Poisonous?

Martha wrote to ask: “Is it true that it is bad, even poisonous, to eat a potato if it turns green?”

This one has some truth to it. Potatoes are members of the nightshade family, along with tomatoes, peppers and eggplants. All of these plants produce a compound called solanine that, when consumed in sufficient amounts, acts as a nerve poison.

The presence of solanine in the leaves and stems of nightshade plants acts as a natural pesticide, dispatching any bugs that nibble too freely on the plant. And even though you’re a lot bigger than that bug, the amount of solanine in potato or tomato leaves might be enough to give you an upset stomach, which is why we don’t eat those parts of the plant.

The fruits of nightshade plants—potatoes, tomatoes, peppers and eggplants—generally contain very low levels of solanine, which is why they are safe to eat. But potatoes with greenish skin or with eyes that have started to sprout may contain enough solanine to cause a problem. Best to discard them.

Should People with Arthritis Avoid Nightshades?

By the way, you sometimes hear that people with arthritis should avoid nightshade plants because they cause inflammation and joint pain. That’s partially true. Some people are highly sensitive to solanine and for these folks, eating tomatoes and peppers can cause swelling and pain in the joints.

If you have joint pain or arthritis, try eliminating all nightshade plants from your diet for two or three weeks and see whether it makes any difference. If it does, you may be one of those people who is sensitive to solanine. If you don’t notice any improvement when you cut out nightshades, then there is no need to avoid these otherwise healthy foods.

Does Eating at Night Make You Gain Weight?

Wendy writes: "My fiancé is convinced that eating late at night causes the food to turn into fat while you are sleeping faster than it would while you are awake. I don't see how this is possible. Does the time of day you eat your meals have any effect on how they are digested?"

This is one of those things that seems so logical—but isn’t. Food has the same number of calories, regardless of whether you are sleeping or awake while you digest it. Cutting down on late-night snacking can be an effective strategy for weight maintenance, but it doesn’t have anything to do with how your body metabolizes calories.

It’s simply that snacking in the evening is usually recreational eating—extra calories that we pile on after the day’s nutritional needs have been met. Also, a lot of people find that their self-control is lower in the evening and they end up eating more than they mean to or indulging in foods that they wouldn’t choose in the bright light of day.

It’s the extra calories that lead to weight gain, not the time of day they’re eaten.

Does Your Body Absorb Nutrients from Supplements?

Calvin writes: “Of the many vitamins and minerals that are added to foods to enrich them, which of them are actually absorbed by the body? I had a friend in college who had a Ph.D. in nutrition and she told me that many of these additives are actually passed out in the urine.”

We know that nutrients that are added to fortify foods get absorbed because fortification programs work. When we started adding folic acid to flour and cereal, for example, the incidence of birth defects like Spina bifida—which is caused by folic acid deficiency—went way down.

Likewise, the introduction of iodized salt drastically reduced the number of people walking around with goiters, which are caused by iodine deficiency. Fortifying milk with vitamin D made rickets largely obsolete. That’s not to say that fortification programs are perfect or that they never have unintended consequences. But that’s a subject for a different article!

Likewise, when people take vitamin supplements, you can usually measure an increase in the level of nutrients in their blood and tissues. But it’s also not uncommon for nutrients to spill over into the urine, especially if the supplements contain doses that are simply higher than the body can absorb or use.

For example, when you take calcium supplements, you excrete more calcium, but that doesn’t mean you’re not absorbing any calcium. You’re just not absorbing all of it.

Supplements have their place, and I’ve talked about the role of multivitamins and other nutrients in previous articles. But, in general, I think it’s best to get as much of your nutrition as possible from whole foods. That way, you’re most likely to get the nutrients in the forms, amounts, and combinations that your body can make the best use of.

Keep in Touch

Thanks for these and all the other great questions and topics you’ve sent in over the last two years. Your curiosity about nutrition and enthusiasm for eating well and feeling fabulous is what makes my job so much fun!

If you have a nutrition question, try searching my Nutrition Diva archives. After two years of weekly columns, chances are good that I’ve addressed it at some point.

About Monica Reinagel, The Nutrition DivaMonica Reinagel is a board-certified Licensed Nutritionist and a professionally-trained chef. She is the host of the Nutrition Diva podcast which is part of the Quick and Dirty Tips network. She has authored three books on health and nutrition, developed recipes and diet plans for websites and other publications. Monica's professional affiliations include the American Dietetic Association, the International Association of Culinary Professionals and the American Guild of Musical Artists.

Reprinted by arrangement with Quick and Dirty Tips, a division of Macmillan Holdings, LLC.